In recent years, a moving-picture coding method in which encoding efficiency is greatly improved has been recommended as ITU-T REC. H.264 and ISO/IEC 14496-10 (hereinafter referred to as “H.264”) jointly with ITU-T and ISO/IEC. H.264 does not rely on a prediction processing method but performs the processes of an orthogonal transformation and an inverse orthogonal transformation using a discrete cosine transformation.
For instance, WO 2008/157431 and M. Karczewicz, “Improved intra coding”, ITU-T SG16/Q.6, VCEG Document, VCEG-AF15, April 2007 disclose a method for improving encoding efficiency by expanding an orthogonal transformation and an inverse orthogonal transformation in H.264, by providing each of the nine types of prediction direction determined as intra-prediction modes with a transformation basis designed to increase coefficient density after an orthogonal transformation of a generated predictive residual, and by performing an orthogonal transformation and an inverse orthogonal transformation.
However, the methods described in WO 2008/157431 and M. Karczewicz, “Improved intra coding”, ITU-T SG16/Q.6, VCEG Document, VCEG-AF15, April 2007 mentioned above require an orthogonal transformation processes differing according to each intra-predation mode. To realize the methods by using hardware, eight types of configuration of hardware dedicated for orthogonal and an inverse orthogonal transformation are required, in addition to hardware dedicated to a discrete cosine transformation and an inverse discrete cosine transformation as required in H.264. As a result, circuit scale increases.